Add Gitlab CI config file

8 jobs for master in 18 minutes and 24 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Build
passed #416574
build

00:03:24

 
  Test
passed #416579
autopkgtest

00:02:42

passed #416580
blhc

00:01:12

passed #416578
allowed to fail
lintian

00:01:32

passed #416581
piuparts

00:03:19

passed #416577
reprotest

00:02:13

passed #416576
test-build-all

00:02:59

passed #416575
test-build-any

00:02:10